GRRRR - Suspected Head Gasket Failure

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davidimurray

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posted on 17/10/15 at 05:13 PM

GRRRR - Suspected Head Gasket Failure

Haven't used the car for a few weeks pushed it out the garage to move a few things around the garage. Turned the ignition on and fuel pump never stopped running, followed by a pool of petrol on the floor. Got the car back in quickly and found petrol dripping out of the airbox. But then with the bonnet off I noticed a header tank with a layer of mayo inside it. Oil is spotless.

So I am guessing that the head gasket has let go. The annoying thing is that I rebuilt the engine, Duratec, only 1000 miles ago and fitted a new headgasket and studs then.

Any thoughts on why it might have failed so quickly. Mating faces were immaculate so I can only think that because I built the engine on a stand and torqueing them down was a challenge without the engine moving around.

Cheers

Dave

JoelP

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posted on 17/10/15 at 05:51 PM

I might be missing something, but why would a head gasket failure cause a fuel leak? Or is that a separate fault?

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mark chandler

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posted on 17/10/15 at 05:52 PM

Mayo could just be short use, starting and moving around a lot, a decent drive would stop it happening as it's just condensation.

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posted on 17/10/15 at 05:58 PM

You have a fuel leak which doesn't allow the HP pump to pressurise the system....sort that and you'll be fine !

davidimurray

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posted on 17/10/15 at 06:21 PM

Two separate issues.

Pretty sure the fuel problem is a stuck float in one of the carbs.

rusty nuts

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posted on 17/10/15 at 06:28 PM

Before taking the head off try using a block tester

40inches

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posted on 17/10/15 at 06:43 PM

Had a blown head gasket twice over the years, on both occasions starting the engine without the header cap on looked as though someone had dumped a packet of Alka-Seltzer in the header tank.
I'm with Mark, give it a decent run, the Mayo will most likely disappear

davidimurray

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posted on 17/10/15 at 06:59 PM

I can understand mayo in the oil being due to condensation and a good run clearing it out, but if it is in the header tank then there should not be any way for the oil to mix with the water.

If there was leak between the oil return/water galleries then I would think the higher water pressure would show up as mayo in the sump/rocker cover. I am guessing that mine is a leak between the oil pressure feed and water gallery as the oil pressure will be higher than the water pressure.

The cooling system is sealed and pressurised so surely any 'mayo' in there will not boil off/clear but just move around the system?

Rusty Nuts - can you explain what you mean by a block tester?

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posted on 17/10/15 at 07:07 PM

Only two possible causes of the mayo in the water side either oil left in the waterways during the build or oil leaking under pressure through the head gasket.
I would accept the former until proved other wise.

A block test is a chemical test for exhaust gases on the water side of the system, it won't show anything unless the gasket is leaking combustion gases past the fire rings.

Head gasket problems are usually notoriously difficult to diagnose.

[Edited on 17/10/15 by britishtrident]

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MikeRJ

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posted on 17/10/15 at 07:37 PM

Does the car have a water/oil heat exchanger? It's not unknown for them to leak internally and cause water/oil mixing.

davidimurray

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posted on 17/10/15 at 08:33 PM

Thanks all - will get the fuelling sorted, see what I can clean from the header tank and then give her a run.

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